DE102006021405B4 - Illumination system in a microwave imaging system, microwave imaging system and method for acquiring a microwave image - Google Patents

Abstract

An illumination system (100) in a microwave imaging system (10) for illuminating an antenna array (50) comprising antenna elements (80) for directing microwave illumination to and from a target (155) to capture a microwave image of an object (150) the antenna array (50) comprises subarrays (60) of the antenna elements (80) arranged in a sparse geometry to form complementary subarray structures (90a, 90b) of the antenna array (50), the illumination system (100) comprising the following features a transmitter (130) operable to transmit microwave illumination at frequencies between 1 GHz and 1000 GHz to the antenna array (50); a receiver (135) operative to receive microwave illumination reflected by the antenna array (50) reflected from the target (155); and an illumination network (140) operable in a first mode to transmit the microwave illumination (20) from the transmitter (130) to both of the complementary structures (90a, 90b) of the antenna array (50) and the reflected .. ,

Description

Recent advances in microwave imaging have enabled the commercial development of microwave imaging systems capable of producing two-dimensional and even three-dimensional microwave images of objects and other elements of interest (e.g., human subjects). Currently, several microwave imaging techniques are available. For example, one technique uses an array of microwave detectors (hereinafter referred to as "antenna elements") to detect either passive microwave energy emitted by the target or reflected microwave energy reflected from the target in response to active microwave illumination of the target. A two-dimensional or three-dimensional image of a person or other element is constructed by scanning the array of antenna elements for the position of the target and / or adjusting the frequency (or wavelength) of the microwave energy being transmitted or detected.

Transmitting and / or receiving antenna arrays for use in transmitting and / or receiving microwave energy may be constructed using conventional analog phase arrays or binary reflector arrays. For each type of array, the largest addressable volume with the highest spatial resolution is obtained by choosing a small wavelength, λ that densely fills the array with antenna elements, so that the spacing between adjacent antenna elements in both directions is λ / 2, and maximizing the two-dimensional area of the array. For example, if the array is a square with the side L, an object located at a distance L from the array may be detected at a resolution of about λ.

The number of antenna elements and therefore the cost of the array are proportional to (L / λ) ² . This quadratic cost-dependency is an obstacle in both scaling up the size of an array to increase the addressable field of view, and reducing the wavelength to increase the resolution. As used herein, the term "addressable field of view" (AFOV) refers to the volume that is addressable with high resolution (ie, the volume that can be resolved within a specified highest resolution factor).

One solution proposed for the cost-resolution AFOV problem is using a sparse antenna array as opposed to a densely populated antenna array. As the resolution increases with the numerical aperture, which depends on the diameter and not on the area of the array, an array with two or four antenna elements spaced by L can achieve the desired resolution. Weakly occupied arrays, however, produce multi-lobed antenna structures. If the array is a conventional transmit phased array and 1 ≥ s ≥ 0 is the weak-set factor, Parseval's Theorem of Fourier analysis indicates that only s of the transmit power falls within an area that is originally dense (s = 1). Array of the same extent dissolves. If the sparse array is a reflector array and a transmit horn illuminates the full extent of the originally densely populated (s = 1) array, the sparse array only processes s of the power of the horn. Therefore, the efficiency factor (ie, the fractional fraction that fills the original area) is s ² . If the reflector array is used to direct both the microwave illumination to the target and to receive reflected microwave illumination from the target, the overall efficiency factor is η = s ⁴ . For example, a 50% sparse reflector array produces a transmit-to-receive efficiency of 1/16 = 6.25%. Thus, as the low occupancy of the array increases, signal loss increases with the fourth power.

The signal-to-noise (SNR) ratio of a sparse array suffers from the same s ² or s ⁴ dependence. In addition, background noise (often referred to as "clutter") resulting from stray radiation also increases SNR for sparse arrays for several reasons. First, the unoccupied area of the original densely packed (s = 1) array becomes a collective plane mirror, which bounces off the radiation with a filling factor efficiency of 1 s. Second, the remaining (occupied) surface geometry generally produces sidelobes that change direction in a poorly controlled manner as the antenna phasing changes. Side lobe weight increases as the low occupancy of the array increases. To the extent that these two factors increase system noise as the array becomes sparse, SNR varies empirically as s ^a / (1-s) ^b , where a ≈ 4 and b ≈ 1. Thus, sparsely populated arrays increase the Signal loss and an increase in SNR.

From the WO 00/63720 A2 already an image acquisition system with a sparse antenna array is known, which works with millimeter waves. The known system has an electronic mirror.

What is needed, therefore, is a microwave imaging system for use with sparse antenna arrays that is capable of detecting a microwave image with side lobes suppressed.

It is the object of the present invention to provide an illumination system in a microwave imaging system, a microwave imaging system, and a method for acquiring a microwave image of an object having improved characteristics.

This object is achieved by systems according to claim 1 and 17 and a method according to claim 25.

Embodiments of the present invention provide an illumination system in a microwave imaging system for illuminating a sparse antenna array to detect a microwave image of a target with side lobes suppressed. The sparse antenna array includes antenna elements for directing microwave illumination to and from the target by placing the antenna elements in subarrays in a sparse geometry to form complementary subarray structures thereof. The illumination system includes a transmitter operative to transmit microwave illumination to the antenna array, a receiver effective to receive microwave radiation reflected from the antenna array reflected from the target, and an illumination network operating in two modes is to allow sidelobe suppression.

The illumination network is operative in a first mode to transmit microwave illumination from the transmitter to both the complementary structures of the antenna array and to provide reflected microwave illumination from both complementary subarray structures of the antenna array to the receiver. The lighting network is further operative in a second mode to provide microwave illumination from the transmitter to a first of the complementary subarray structures of the antenna array and to provide reflected microwave illumination from a second of the complementary subarray structures of the antenna array to the receiver.

Embodiments of the present invention further provide a microwave imaging system that includes an antenna array, an illumination system, and a processor. The antenna array includes a plurality of antenna elements, each of which may be programmed with a respective direction coefficient to direct microwave illumination to and from a target associated with an object. The antenna array further includes subarrays of antenna elements arranged in a sparse geometry to form complementary subarray structures thereof. The illumination system is operative to provide microwave illumination to illuminate both complementary structures of the antenna array and to receive reflected microwave illumination reflected by the target of both complementary subarray structures of the antenna array to produce a first receive signal in a first mode. The illumination system is further operative to provide microwave illumination to illuminate a first of the complementary subarray structures of the antenna array and to receive reflected microwave illumination from a second of the complementary subarray structures of the antenna array to produce a second receive signal in a second mode. The processor is operative to measure a value associated with the target in a microwave image of an object as a linear combination of the first received signal and the second received signal.

In one embodiment, the first receive signal and the second receive signal are complex signals describing a main scan lobe and one or more side lobes. The processor suppresses sidelobes in the microwave image of the target by adding the product of the first receive signal and a first complex multiplier to the product of the second receive signal and a second complex multiplier to effectively enhance the main scan lobes and destructively cancel the sidelobes. The first complex multiplier and the second complex multiplier are selected as a function of the sparse geometry of the antenna array.

Preferred embodiments of the present invention will be explained in more detail below with reference to accompanying drawings. Show it:

1 12 is a schematic diagram of a simplified exemplary microwave imaging system for acquiring a microwave image of a suppressed side lobe object using a sparsely populated antenna array in accordance with embodiments of the present invention;

2A FIG. 4 is a pictorial representation of an exemplary sparse antenna array design in accordance with embodiments of the present invention; FIG.

2 B a pictorial representation of another exemplary sparse antenna array according to embodiments of the present invention;

3A a schematic diagram of an exemplary lighting system, which in the Is able to operate in multiple illumination modes for use with the microwave imaging system of the present invention;

3B a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

4A to 4C pictorial representations of the exemplary phase plates for use in the in 3A and 3B exemplary lighting systems shown;

5 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

6 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

7 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

8th a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

9 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention;

10 12 is a schematic diagram of another simplified exemplary microwave imaging system for acquiring a microwave image of a suppressed side lobe object using a sparse antenna array, in accordance with embodiments of the present invention;

11 a schematic diagram of an exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of FIG 10 ;

12 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of FIG 10 ;

13 a schematic diagram of another exemplary illumination system capable of operating in multiple illumination modes for use with the microwave imaging system of FIG 10 ;

14 a graphical representation of exemplary amplitude product distributions for different illumination modes;

15 5 is a flowchart illustrating an example process for acquiring a microwave image of a target of an object, according to embodiments of the present invention;

16 a flow chart illustrating an exemplary process for acquiring a microwave image of an object according to embodiments of the present invention; and

17 5 is a flowchart illustrating another exemplary process for acquiring a microwave image of an object according to embodiments of the present invention.

As used herein, the terms microwave radiation and microwave illumination respectively refer to the band of electromagnetic radiation having wavelengths between 0.3 mm and 30 cm, which corresponds to frequencies from about 1 GHz to about 1000 GHz. Thus, the terms microwave radiation and microwave illumination respectively include conventional microwave radiation, as well as what is conventionally known as millimeter wave radiation.

1 FIG. 12 is a schematic diagram of a simplified exemplary microwave imaging system. FIG 10 according to embodiments of the present invention. The microwave imaging system 10 includes one or more sparse antenna arrays 50 (For convenience, only one is shown), a microwave lighting system 100 , a processor 110 , a store 160 and an ad 120 , The sparse antenna array 50 is able to transmit microwave lighting and / or microwave lighting via antenna elements 80 to receive a microwave image of an object 150 (for example, a suitcase, a human person, or any other element of interest). Each antenna element 80 is with a certain direction coefficient (eg reflection coefficient or transmission coefficient) programmed to microwave radiation to and / or from a target 155 on the object 150 to judge. The antenna elements 80 may each be any type of microwave antenna, including, but not limited to, patch, dipole, monopole, loop, and dielectric resonator type antennas.

The sparse array 50 is a passive programmable array made up either of reflector antenna elements 80 or transmitting antenna elements 80 consists. In a reflection mode, each of the reflector antenna elements is 80 capable of being programmed with a respective reflection coefficient, to microwave radiation to the target 155 on the object 150 to reflect that is captured. The reflection coefficient may represent a binary or continuous phase delay or an amplitude variation. For example, the microwave lighting that passes through the sparse antenna array 50 from the microwave lighting system 100 is received, to the destination 155 on the object 150 reflected, and the reflected microwave lighting coming from the target 155 is reflected and by the sparse antenna array 50 is received, becomes the microwave lighting system 100 reflected by programming each of the individual reflector antenna elements 80 with a respective reflection coefficient.

In a transmission mode, each of the transmitting antenna elements is 80 being able to be programmed with a respective transmission coefficient to microwave lighting to the target 155 on the object 150 to be judged. For example, microwave lighting is used by the sparse antenna array 50 from the microwave lighting system 100 is received through the array 50 and to the destination 155 on the object 150 directed, and reflected microwave lighting from the target 155 is reflected and by the sparse antenna array 50 is received through the array 50 and to the microwave lighting system 100 by programming each of the individual transmit antenna elements 80 with a respective transmission coefficient.

The antenna elements 80 in the sparse antenna array 50 are in subarrays 60 divided, each one or more of the antenna elements 80 include. The subarrays 60 are also on the array 50 arranged in a sparse geometry to complementary subarray structures 90a and 90b to form the same. The complementary structures 90a respectively. 90b create complementary microwave beam structures at the target 155 , The microwave image of the target 155 is formed at the interface of the complementary microwave beam structures.

The lighting system 100 includes a transmitter 130 , a receiver 135 and a lighting network 140 capable of operating in two different illumination modes (hereinafter referred to as connected and separate modes) for suppressing side lobes in the microwave image of the object 150 to enable. The lighting network 140 includes phase plates or generalized lenses combined with microwave horns to provide the connected and separate illumination of the array 50 to create. Various lighting networks 140 are in connection with 5 - 13 shown and described in detail.

In the connected mode, the subarrays become 60 in both complementary subarray structures 90a and 90b illuminated, by both the transmission of the transmitter 130 as well as the receiving feeder of the receiver 135 , Thus, in the connected mode, the microwave lighting becomes 20 from the transmitter 130 via the lighting network 140 to both of the complementary subarray structures 90a and 90b of antenna elements 80 transmitted, and reflected microwave lighting 40 from both complementary subarray structures 90a and 90b the antenna elements 80 is via the lighting network 140 at the receiver 135 receive. In the disconnected mode, the subarrays 60 in a first complementary subarray structure 90a illuminated by the transmit feeder, and the subarrays 60 in a second complementary subarray structure 90b are illuminated by the receiving feeder. Thus, the microwave lighting 30 in the disconnected mode from the transmitter 130 via the lighting network 140 to one of the complementary subarray structures (eg structure 90a ), and reflected microwave illumination 70 from the other complementary subarray structure (eg

structure 90b ) is via the lighting network 140 at the receiver 135 receive.

More specifically, in the connected mode, the lighting network is aimed 140 the microwave lighting 20 from the transmitter 130 to the antenna elements 80 in both subarray structures 90a and 90b , Based on the directional coefficient in each of the antenna elements 80 programmed, is the microwave lighting 25 from both subarray structures 90a and 90b to the destination 155 directed. The directional coefficients are selected to be a positive disturbance of the microwave lighting 25 from each of the antenna elements 80 at the destination 155 to create. For example, in embodiments where the antenna elements are reflector antenna elements, the phase shift of each of the antenna elements 80 be set to the same phase delay for each path of microwave lighting 25 from the source (antenna element 80 ) to the destination 155 to deliver. The complementary structures 90a and 90b generate complementary transmit microwave beam structures at the target 155 ,

The same applies to reflected microwave radiation 45 that from the goal 155 is reflected, and at the sparse antenna array 50 is received from the antenna elements 80 in both subarray structures 90a and 90b back to the lighting network 140 directed, based on the directional coefficient, in each of the antenna elements 80 is programmed. The complementary structures 90a and 90b generate complementary receive microwave beam structures on the lighting network 140 , The lighting network 140 receives the reflected microwave illumination 40 and provides the reflected microwave illumination 40 from both subarray structures 90a and 90b is received, to the receiver 135 , The recipient 135 combines the reflected microwave illumination 40 from each antenna element 80 in both subarray structures 90a and 90b is reflected to a first received signal (connected signal) 170 to generate the value of the effective intensity of the reflected microwave illumination at the target 155 displays. In one embodiment, the receiver generates 135 the connected signal 170 using the microwave illumination received from the intersection of the complementary receive microwave beam structures. More specifically, the generated connected signal 170 is the volume-integrated cross product of complementary receive microwave rays.

In the disconnected mode, the lighting network is pointing 140 the microwave lighting 30 from the transmitter 130 to the antenna elements 80 in only one of the subarray structures (eg structure 90a ). Based on the directional coefficient in each of the antenna elements 80 in this subarray structure 90a programmed is the microwave lighting 35 from the antenna elements 80 in these subarray structures 90a to the destination 155 directed. Reflected microwave lighting 75 that from the goal 155 is reflected and on the sparse antenna array 50 is received, however, from the antenna elements 80 in the other subarray structures 90b back to the lighting network 140 directed, based on the directional coefficient, in each of the antenna elements 80 in this subarray structure 90b is programmed. Thus, the complementary structures produce 90a and 90b Transmit microwave radiation structures at the target 155 ,

The lighting network 140 receives the reflected microwave illumination 70 and provides the reflected microwave illumination 70 from the antenna elements 80 in the subarray structures 90b is received, to the receiver 135 , The recipient 135 combines the reflected microwave illumination 70 from each antenna element 80 in the subarray structure 90b is reflected to a second received signal (separate signal) 175 to generate the value of the effective intensity of the reflected microwave illumination at the target 155 displays. In one embodiment, the receiver forms 135 the separate signal 175 at the intersection of the complementary transmit and receive microwave beam structures. More specifically, the generated connected signal 170 is the volume integrated cross product of the complementary transmit and receive microwave beams.

Both the connected signal 170 as well as the separate signal 175 be from the recipient 135 to the processor 110 passed the signals 170 and 175 used to determine the value of a pixel or voxel that matches the target 155 on the object 150 equivalent. The signals 170 and 175 Both are complex signals containing real and imaginary parts (or equivalent amplitude and phase) describing a main scan lobe and one or more unwanted sidelobes. Due to the different transmit / receive paths of the two illumination modes, the side lobes in each of the signals 170 and 175 opposite signs. Thus, the processor 110 being able to constructively enhance the main scanning lobe while destructively canceling the unwanted side lobes by calculating an optimum linear combination of the connected signal 170 and the separated signal 175 ,

For example, with reference to 14 an exemplary amplitude product distribution of a separate signal in the graph shown with 1410 is shown, and an exemplary amplitude product distribution of a connected signal is shown in the graph with 1420 is designated. In the 14 The graphs shown were constructed using an array with a sparse geometry similar to that in FIG 2A shown geometry. As can be seen, in both the connected and disconnected modes, in addition to the desired central main lobe, there are four symmetric sets of sidelobes. In the disconnected mode (Graph 1410 ), however, the amplitude of the sidelobes is negative (ie opposite in sign to the main lobe), while in the connected mode (graph 1420 ) the amplitude of the side lobes is not negative (ie the same sign as the central lobe). Thus, forming a superposition of the two distributions 1410 and 1420 with the proper weighting between the two distributions 1410 and 1420 to a distribution with a strong main lobe and weak side lobes, as in the graph 1430 is shown.

With renewed reference to 1 the processor determines 110 the optimal linear combination (weighting) of the connected signal 170 and the separated signal 175 based on the weakness of the array geometry (ie, the complementary subarray structures 90a and 90b ). For example, if the connected signal is labeled J and the separate signal is labeled D, the processor selects 110 complex multipliers (parts by weight) m _J and m _D based on the geometry of the array 50 , such that m _J + m _D = one, and calculates the resulting signal as m _J · J + m _D · D.

In general, the weight percentages assigned to the complex multipliers m _D and m _D are linearly proportional to the weak set-ting of the array 50 , For a fully packed array, the weight given to the connected signal is 100%, and so the value of the complex multiplier m _{J is} one and the value of the complex multiplier m _D is zero. Likewise, for a fully sparse array (eg, a frame geometry as shown in FIG 2A is shown with only a single antenna element per subarray), the weight assigned to the isolated signal is 100%, and thus the value of the complex multiplier _{mJ is} zero and the value of the complex multiplier _mD is one. The values of the complex multipliers m _J and m _D are typically the same for all pixels or voxels in a sample of the object 150 , and therefore the processor can 110 Optimize the values of the complex multipliers once and optimize the values in memory 160 or in the processor 110 store for use during the scan.

In addition, the processor works 110 to the lighting system 100 to control for the connected and separate lighting mode. In one embodiment, the processor switches 110 between the connected and disconnected lighting modes. The processor 110 represents the lighting network 140 for example, on the connected mode to the connected signal 170 to receive, and then sets the lighting network 140 on the disconnected mode to the separate signal 175 to recieve. In another embodiment, the processor controls 110 the transmitter 130 and the receiver 135 to operate substantially simultaneously in both the connected and separate illumination modes.

The processor 110 also operates to calculate the directional coefficients of each of the individual antenna elements 80 in the sparse antenna array 50 to program to multiple goals 155 on the object 150 to illuminate with microwave rays, and / or reflected microwave illumination from multiple targets 155 on the object 150 to recieve. Thus, the processor works 110 in conjunction with the sparse antenna array 50 to the object 150 scan. In operation, the microwave imaging system operates 10 at frequencies that allow for millions of goals 155 sampled per second.

The processor 110 includes any hardware, software, firmware or combination thereof for controlling the sparse antenna array 50 and processing the received microwave lighting from the target 155 is reflected to a microwave image of the target 155 and / or the object 150 build. In one embodiment, the memory stores 160 Software by the processor 110 is executable to the antenna array 50 to control and / or the microwave image of the object 150 build. In another embodiment, the software is in the processor 110 saved, and the memory 160 optionally stores data by the processor 110 while running the software.

The processor 110 For example, it may include one or more microprocessors, microcontrollers, programmable logic devices, digital signal processors, or other types of processing devices configured to execute instructions of a computer program and one or more memories (eg, cache memory) containing the instructions and others Save data by the processor 110 be used. It should be understood, however, that other embodiments of the processor 110 can be used. The memory 160 is any type of data storage device, including but not limited to, a hard disk, a random access memory (RAM), read-only memory (ROM), compact disk, floppy disk, ZIP ^® drive, tape drive, database or other type of storage device or storage medium ,

The resulting microwave image of the target 155 and / or object 150 can from the processor 110 to the ad 120 to display the microwave image. In one embodiment, the display is 120 a two-dimensional display for displaying a three-dimensional microwave image of the object 150 , or one or more one-dimensional or two-dimensional microwave images of the target 155 and / or object 150 , In another embodiment, the display is 120 a three - dimensional display that in the Location is a three-dimensional microwave image of the object 150 display.

It should be clear that several sparse antenna arrays 50 Can be used to different sections of the object 150 scan. For example, the microwave imaging system 10 are implemented with two sparse antenna arrays, each containing a 1m x 1m sparse array of antenna elements 80 exhibit around half of the object 150 scan. As another example, the microwave imaging system 10 with four sparse antenna arrays 50 be implemented, each having a 0.5m x 0.5m sparse array of antenna elements 80 which is capable of a quadrant of the object 150 scan.

Examples of complementary subarray structures 90a and 90b , which is a weak antenna array 50 form, are in 2A and 2 B shown. 2A FIG. 3 illustrates an exemplary "picture frame" structure in which one of the complementary subarray structures 90a hatched subarrays 60 includes, and the other complementary subarray structure 90b empty subarrays 60 includes. In the connected illumination mode, all subarrays are 60 illuminated by both the transmit and the receive feed in the microwave lighting system, while in the separate illumination mode, the subarrays 60 in the first complementary subarray structure 90a are illuminated by the transmit feed and the subarrays 60 in the second complementary subarray structure 90b illuminated by the receiving feeder. The corner subarrays 60 are either split illuminated (through both illumination modes) along the diagonal or not lit at all.

2 B represents an exemplary "cross" structure in which one of the complementary subarray structures 90a the hatched subarrays 60 includes, and the other complementary subarray structure 90b the empty subarrays 60 includes. In the connected illumination mode, all subarrays are 60 is illuminated by both the transmit and receive in the microwave illumination system, while in the separate illumination mode, the subarrays 60 in the first complementary subarray structure 90a are illuminated by the transmit feed, and the subarrays 60 in the second complementary subarray structure 90b illuminated by the receiving feeder. The middle subassembly 60 (ie the sub-assembly 60 , both structures 90a and 90b can be illuminated in both illumination modes, by randomly assigning substantially equal numbers of antenna elements 80 to either the connected mode or the disconnected mode.

In one embodiment, one or more of the subarrays 60 a densely packed subarray of antenna elements 80 , In other embodiments, one or more of the subarrays 90 a weakly occupied subarray of antenna elements 80 , For example, one or more of the subarrays may have a single row or column of densely populated or sparse antenna elements 80 contain. In any case, the complementary subarray structures are 90a and 90b composed of a greatly reduced number of antenna elements, such that the total number of antenna elements 80 in the sparse antenna array 50 is greatly reduced compared to a densely packed array. This reduction in element count results in directly reduced costs. Thus, the cost of the complementary array with reduced element count, such as. B. those in 2A and 2 B , proportional to only the square root of A, which achieves significant cost savings, as opposed to densely packed arrays where the cost of the array is proportional to the footprint A of the densely packed arrays. In addition, AFOV is unchanged between the densely populated array and the complementary array with reduced element count, because the overall extent of the complementary arrays and the minimum spacing is the same as for the originally densely populated array.

3A is a schematic representation of an exemplary lighting system 100 capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. The lighting system 100 includes the lighting network 140 , the transmitter 130 and the receiver 135 , In 3A includes the lighting network 140 microwave horns 310 . 320 and 330 , Phase plates 340 . 342 and 344 , a circulator 350 and switches 360 and 370 for performing RF switching between the two illumination modes. The desk 360 is with the receiver 135 connected and selectively switches between the horn 310 and the circulator 350 , The desk 370 is with the transmitter 130 connected and selectively switches between the horn 330 and the circulator 350 , In 3A are the switches 360 and 370 single-pole switching (SPDT) microwave switches. However, in other embodiments, other types of switches could be used.

The central phase plate 342 is designed to illuminate the entire sparse geometry of both complementary subarray structures in the connected illumination mode. The left phase plate 340 is designed to to illuminate one of the complementary subarray structures in the disconnected mode while the right phase plate 344 is designed to illuminate the other complementary subarray structure in the disconnected mode. The phase plates 340 . 342 and 344 can either by reflection or transmission of microwave lighting to and from the horns 310 . 320 respectively. 330 work. In other embodiments, the horns 310 . 320 and 330 custom designed far field pattern horns, thereby reducing the need for phase plates 340 . 342 and 344 cancel. For example, leaky waveguides, cylindrical lenses, cylindrical mirrors, and other types of custom horns may be used with embodiments of the present invention.

In the connected lighting mode, both switches connect 360 and 370 with the circulator 350 to transmit microwave radiation through the middle horn 320 to send and receive to generate the connected signal. In the separate illumination mode, the switch connects 360 with the horn 310 , and the switch 370 connects to the horn 330 to microwave radiation completely through the right horn 330 to transmit and microwave radiation completely through the left horn 310 to receive the separate signal. In one embodiment, the microwave imaging system is a coherent system, and thus narrowband. Therefore, the switches can 360 and 370 be designed as a narrowband switch to obtain a performance with less insertion loss than that achievable with universal broadband microwave switches. As a result, any of the configurations of the lighting system shown herein may be used 100 be used with relatively low transmission power.

3B FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave lighting system of the present invention. The lighting system 100 includes the lighting network 140 , the transmitter 130 and the receiver 135 , In 3B includes the lighting network 140 only a single microwave horn 320 , a corresponding phase plate 342 and a circulator 350 , The phase plate 342 is designed to illuminate the entire sparse geometry of both complementary subarray structures in both the connected illumination mode and the separate illumination mode. The two illumination modes (connected and disconnected) are implemented digitally on the antenna array by inverting the phase shifts of the individual antenna elements in one of the complementary subarray structures, while maintaining the phase shifts of the individual antenna elements in the other complementary subarray structure.

For example, in a binary array, each antenna element may be programmed with only one of two different binary states (eg, 0 degrees phase shift or 180 degrees phase shift). In the separate illumination mode, the antenna elements in both complementary subarray structures are first programmed with a respective phase shift (0 or 180 degrees) designed to cause constructive interference of the reflected microwave illumination at the receiver 135 to create. In the isolated illumination mode, the phase shift of each of the antenna elements in only one of the complementary subarray structures is reversed (inverted) such that if a particular antenna element is programmed with 0 degree phase shift during the connected illumination, the phase shift of that particular antenna element for one separate lighting is changed to 180 degrees. As an example, with reference to 2A , the phase shifts of the antenna elements in the subarray structure 90a in the separate illumination mode while the same phase shifts of the antenna elements in the subarray structure 90b to be kept.

As a result, the received microwave radiation reflected from the object and through the antenna array to the illumination system 100 two independent channels, referred to herein as a "plus" channel and a "minus" channel. The plus channel is equivalent to the connected illumination channel measured by the reflected microwave radiation received during the connected illumination mode. The minus channel is obtained by inverting the phase shifts of one of the subarray structures during the separate illumination mode. However, the minus channel is not equivalent to the separate illumination channel. Instead, the separate illumination channel is equivalent to the difference between the plus channel and the minus channel.

The separate channel may also be referred to as a "mixed" signal, while the addition of the plus and minus channels may be referred to as a "pure" signal. Any suitable linear combination of the plus channel signal and the minus channel signal or the pure channel signal and the mixed channel signal produces the optimum sidelobe cancellation.

4A - 4C are pictorial representations of exemplary phase plates 340 . 342 and 344 for use in exemplary lighting systems incorporated in 3A and 3B are shown. In 4A - 4C are the phase plates 340 . 342 and 344 binary phase zone plates, while white areas represent 0 degree phase shift zones and black areas represent 180 degree phase shift zones. In other embodiments, the phase plates are 340 . 342 and 344 quaternary phase plates (0 °, 90 °, 180 ° and 270 °) or continuous phase plates, such. A conventional Fresnel lens or ordinary lens. The particular phase shift zone structure on the phase plates 340 . 342 and 344 depends on the complementary subarray structures of the array. For example, the "picture frame" structure used in 2A is shown to require different phase plates than the "cross" structure shown in FIG 2 B is shown.

Generally, the phase plates 340 and 344 for illuminating the individual complementary subarray structures almost complementary (orthogonal) to each other to provide the proper phase shift between the transmit and receive beam structures in the separated mode. The phase plate 342 for connected lighting, self-doubling, ie, a geometric operation (eg, 90 ° rotation), is the left-hand plate 340 to the right panel 344 converts leaves the center plate 342 unchanged.

5 FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. at 5 includes the lighting network 140 two microwave horns 510 and 520 , a variable phase plate 530 , a solid-phase plate 540 , a circulator 550 and a switch 560 for performing RF switching between the two illumination modes. The desk 560 is with the transmitter 130 connected and selectively switches between the horn 520 and the circulator 550 , The recipient 135 is with the circulator 550 connected to the horn 510 is connected and selectively with the switch 560 connected is.

The variable phase plate 530 is designed to illuminate the entire sparse geometry of both complementary subarray structures in the connected illumination mode and one of the complementary subarray structures in the discrete mode, while the solid phase plate 540 is designed to illuminate the other complementary subarray structure in the disconnected mode. In the connected illumination mode is the variable phase plate 530 programmed to illuminate the entire sparse geometry of both complementary subarray structures of the antenna array, and the switch 560 is with the circulator 550 connected to microwave radiation through the left horn 510 and the variable phase plate 530 to send and receive to generate the connected signal.

In the separate illumination mode, the switch is 560 with the horn 520 and the solid-phase plate 540 connected to microwave radiation through the horn 520 and the solid-phase plate 540 to translate one of the complementary subarray structures, and the variable phase plate 530 is programmed to illuminate the other complementary subarray structures to microwave radiation through the variable phase plate 530 and the horn 510 to receive the separate signal. It should be clear that the transmitter 130 and the receiver 135 can be replaced if the circulator 550 left-right-mirrored. Although it seems like using a single switch 560 unlike in 3 and 6 - 9 shown several switches a poor insulation performance of the switch 560 generate, supplies the circulator 550 Isolation to compensate for the poor isolation performance of the switch 560 and therefore, any type of microwave switch can be used. Conversely, the insertion loss of the switch 560 compared to 3 and 6 - 9 relaxed.

In another embodiment, the variable phase plate is 530 replaced by a solid-phase plate that illuminates the entire sparse geometry of the complementary subarray structures. When the switch 560 with the circulator 550 connects, the connected illumination mode operates in the same way as described above. When the switch 560 with the horn 520 However, the separate lighting mode is implemented with an efficiency penalty factor of two.

6 FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. In 6 includes the lighting network 140 two microwave horns 610 and 620 , Phase plates 630 and 640 , a 50/50 power divider / combiner 650 , a circulator 660 , an optional phase shifter 670 and switches 680 . 685 . 690 and 695 for performing RF switching between the two illumination modes. The desk 680 is with the receiver 135 connected and selectively switches between the circulator 660 and an outer transmission line to the horn 610 , The desk 685 is with the transmitter 130 connected and switched selectively between an external transmission line to the horn 620 and the circulator 660 , The desk 690 is with the horn 610 and selectively switches between the outer transmission line to the receiver 135 and the power divider 650 , The desk 695 is with the horn 620 and selectively switches between the outer transmission line to the transmitter 130 and the power divider 650 (via the optional phase shifter 670 ).

A phase plate 630 is designed to illuminate one of the complementary subarray structures, while the other phase plate 640 is designed to illuminate the other complementary subarray structure. In the connected lighting mode, the switches are 680 and 685 with the circulator 660 connected, and the switches 690 and 695 are with the power divider 650 connected so that the microwave radiation is both sent 50/50 and receive 50/50, between the two horns 610 and 620 and corresponding phase plates 630 and 640 to generate the connected signal. If the subarray structure partial lighting from the horns 610 and 620 are exactly complementary, there is no disturbance on the array and the phase shifter 670 is unnecessary. However, if there is a residual overlap of the sublights, the phase shifter can 670 adjusted to optimize the lighting in the overlap regions.

In the separate illumination mode, the switches are 680 . 685 . 690 and 695 connected to the outer transmission lines to the horn 610 with the receiver 135 to connect and the horn 620 with the transmitter 130 to connect to the microwave radiation completely through the horn 620 and the phase plate 640 to transmit and the microwave radiation completely through the horn 610 and the phase plate 630 to receive the separate signal. It should be clear that the transmitter 130 and the receiver 135 can be replaced if the circulator 660 left-right-mirrored.

7 FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. In 7 includes the lighting network 140 two microwave horns 710 and 720 , Phase plates 730 and 740 , a 90 ° hybrid coupler 750 and switches 760 . 765 . 770 and 775 for performing RF switching between the two illumination modes. The desk 760 is with the receiver 135 and selectively switches between an external transmission line to the horn 710 and the lower left arm 752 of the 90 ° hybrid connector 750 , The desk 765 is with the transmitter 130 and selectively switches between an external transmission line to the horn 720 and the lower right arm 754 of the 90 ° hybrid coupler 750 , The desk 770 is with the horn 710 and selectively switches between the outer transmission line to the receiver 135 and the upper left arm 756 of the 90 ° hybrid coupler 750 , The desk 775 is with the horn 720 and selectively switches between the outer transmission line to the transmitter 130 and the upper right arm 758 of the 90 ° hybrid coupler 750 ,

A phase plate 730 is designed to illuminate one of the complementary subarray structures, while the other phase plate 740 designed to shed light on the other complementary subarray structure. In the separate illumination mode, the switches are 760 . 765 . 770 and 775 connected to the outer transmission lines to the horn 710 with the receiver 135 to connect, and to the horn 720 with the transmitter 130 to connect to the microwave radiation completely through the horn 720 and the phase plate 740 to transmit, and the microwave radiation completely through the horn 710 and the phase plate 730 to transmit the separate signal.

In the connected lighting mode, the switches are 760 and 765 with the respective lower arms 752 and 745 of the 90 ° hybrid coupler 750 connected, and the switches 770 and 775 are with the respective upper arms 756 and 758 of the 90 ° hybrid coupler 750 connected. Microwave radiation from the transmitter 130 enters the lower right arm 754 of the 90 ° hybrid coupler 750 one and will be 50/50 from the two upper arms 756 and 758 to the horns 710 and 720 transfer. The microwave radiation coming from the upper left arm 756 is output, 90 degrees with respect to the microwave radiation is rotated, that of the upper right arm 758 is issued.

The received microwave radiation reflected from the object and through the antenna array to the illumination system 100 is directed, includes four different channels: LOL, ROR, LOR and ROL, where L is the left horn 710 R is the right horn 720 and O is the object being imaged. The LOL and ROR channels are "pure" channels, and the LOR and ROL channels are "mixed" channels. All four channels are connected to the lighting network 140 in phase with each other provided an optional phase shifter (not shown) is set correctly. The 90 ° hybrid coupler 750 however, only delivers the "pure" channels to the receiver 135 due to the 90 ° phase shift between the arms. The "mixed" channels are returned to the transmitter 130 conducted and not received. Because the "mixed" channels are essentially equivalent to the separate mode signal, however, the connected signal ("pure" + "mixed") can be calculated from a simple linear combination of the "pure" channel signal and the separate signal obtained during the separate illumination mode.

8th FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. at 8th includes the lighting network 140 two microwave horns 810 and 820 , Phase plates 830 and 840 , a 50/50 power divider / combiner 850 , Circulators 860 . 865 and 870 , and switches 880 and 980 for performing RF switching between the two illumination modes. The desk 880 is with the receiver 135 connected and selectively switches between the circulator 860 and the circulator 865 , The desk 890 is with the transmitter 130 connected and selectively switches between the circulator 870 and the circulator 865 , The circulator 860 is with the horn 810 connected and the circulator 870 is with the horn 820 connected. The power divider 850 is with the circulators 860 . 865 and 870 connected.

A phase plate 830 is designed to illuminate one of the complementary subarray structures, while the other phase plate 840 is designed to illuminate the other complementary subarray structure. In the connected lighting modes are the switches 880 and 890 with the circulator 865 connected so that microwave radiation 50/50 between the two horns 810 and 820 over the circulator 865 and the power divider 850 transmitted directly through the circulator 860 , and by rebounding the reflective open switch terminal to the circulator 870 , Microwave radiation will also be 50/50 between both horns 810 and 820 received, directly through the circulator 870 and by bouncing off the reflective open switch port on the circulator 860 to generate the connected signal.

In the separate illumination mode, the switches are 880 and 890 with the circulators 860 respectively. 870 connected to the horn 810 with the receiver 135 to connect and the horn 820 with the transmitter 130 to connect, and the microwave radiation completely through the horn 820 and the phase plate 840 to transmit, and to microwave radiation completely through the horn 810 and the phase plate 830 to receive the separate signal. An optional phase shifter may also be included to optimize the illumination in the overlap regions.

9 FIG. 12 is a schematic diagram of another exemplary lighting system capable of operating in multiple illumination modes for use with the microwave imaging system of the present invention. FIG. at 9 includes the lighting network 140 two microwave horns 910 and 920 , Phase plates 930 and 940 , a 90 ° hybrid coupler 950 , Circulators 960 and 970 and switches 980 and 990 for performing RF switching between the two illumination modes. The desk 980 is with the receiver 135 connected and selectively switches between the circulator 960 and the lower left arm 952 of the 90 ° hybrid coupler 950 , The desk 990 is with the transmitter 130 connected and selectively switches between the circulator 970 and the lower right arm 954 of the 90 ° hybrid coupler 950 , The circulator 960 is with the horn 910 and the upper left arm 956 of the 90 ° hybrid coupler 950 connected. The circulator 970 is with the horn 920 and the upper right arm 958 of the 90 ° hybrid coupler 950 connected.

A phase plate 930 is designed to illuminate one of the complementary subarray structures, while the other phase plate 940 is designed to illuminate the other complementary subarray structure. In the separate illumination mode, the switches are 980 and 990 with the circulators 960 respectively. 970 connected to the horn 910 with the receiver 135 to connect and the horn 920 with the transmitter 130 to connect to the microwave radiation completely through the horn 920 and the phase plate 940 to transmit and the microwave radiation completely through the horn 910 and the phase plate 930 to receive the separate signal. In the connected lighting mode, the switches are 980 and 990 with the respective lower arms 952 and 945 of the 90 ° hybrid coupler 950 connected to the microwave radiation 50/50 between both horns 910 and 920 to transfer it as related to above 7 is described to generate the connected signal.

10 FIG. 10 is a schematic diagram of another simplified exemplary microwave imaging system. FIG 10 for acquiring a microwave image of an object 150 with suppressed side lobes, a weak antenna array 50 used according to embodiments of the present invention. This in 10 shown microwave imaging system 10 is similar to the one in 1 shown microwave imaging system 1 except that the lighting system 100 two transceivers 1010 and 1020 , each comprising a transmitter and receiver, and the lighting network 140 connected illumination optics 1030 and separate illumination optics 1040 includes.

A transceiver (eg transceiver 1010 ) illuminates the sparse array 50 through the connected illumination optics 1030 (eg horns and phase plates) while the other transceiver 1020 the sparse array 50 through the separate illumination optics 1040 illuminated. Thus, in the connected mode, the subarrays are 60 in both complementary subarray structures 90a and 90b illuminated, both by the transmitting feeder and the receiving feeder of the transceiver 1030 , In the disconnected mode, the subarrays are 60 in a first complementary subarray structure 90a through the transmission feed of the transceiver 1020 illuminated, and the subarrays 60 in a second complementary subarray structure 90b are through the receiving feeder of the transceiver 1020 illuminated. The processor 110 acts as a controller and switches between the transceivers 1010 and 1020 ,

In another embodiment, the connected illumination optics 1030 and the separate illumination optics 1040 combined, as in 6 or 7 to send it to both receivers in the transceiver 1010 and 1020 to allow to receive at all times. The processor 110 switches between the transmit (connected versus disconnected) modes, either with a transmitter (such as a single transmitter, as in 6 or 7 shown), or between the two transmitters of the transceivers 1010 and 1020 , in the 10 are shown. Through the two modes, the two receivers receive four different complex values (2 receivers × 2 modes) stored in the processor 110 can be combined linearly to form the final signal.

11 FIG. 10 is a schematic diagram of an example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system 10 from 10 , at 11 includes the lighting system 100 two receivers 135a and 135b , a transmitter 130 , Microwave horns 1110 and 1120 , Phase plates 1130 and 1140 , Circulators 1150 and 1160 , a 50/50 power divider / combiner 1170 , an optional phase shifter 1180 and switches 1190 and 1195 for performing RF switching between the two illumination modes. The circulator 1150 is with the horn 1110 , the recipient 135a and the power divider 1170 connected. The circulator 1160 is with the horn 1120 and the receiver 135b connected. The desk 1190 is with the transmitter 130 connected and selectively switches between the power divider 1170 and an outer transmission line to the horn 1120 , The desk 1195 is with the circulator 1160 connected and selectively switches between the outer transmission line between the horn 1120 and the transmitter 130 and the power divider 1170 ,

A phase plate 1130 is designed to illuminate one of the complementary subarray structures, while the other phase plate 1140 is designed to illuminate the other complementary subarray structure. In the separate lighting mode, the switches connect 1190 and 1195 with the transmission line, which is the transmitter 130 and the urine 1120 connects, and only the signal from the receiver 135a is selected to generate the separated signal. The signal from the receiver 135b is ignored. In the connected lighting mode, the switches are 1190 and 1195 with the power divider 1170 connected so that the microwave radiation both between the two horns 1110 and 1120 and the corresponding phase plates 1130 and 1140 sent 50/50 and receive 50/50 will, and at both receivers 135a and 135b is received to generate two connected signals (connected R1 and connected R2). The processor determines the value of a pixel or voxel corresponding to the target by forming a corresponding complex linear combination of the three signals (separated, connected R1 and connected R2). When the switches 1190 and 1195 only in the transmit path (and not in the receive path), any switch insertion loss can be overcome by increasing the transmit power without violating broadcast power rule bounds.

12 FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes for use with the microwave imaging system 10 from 10 , In 12 includes the lighting system 100 two transceivers 1010 and 1020 , each one a respective recipient 135a and 135b and a respective transmitter 130a and 130b , a phase lock 1270 to the phase lock transmitters 130a and 130b , connected optics 1030 and separate optics 1040 include. The connected optics 1030 includes a microwave horn 1210 , a phase plate 1230 and circulator 1250 , The separate optics 1040 includes a microwave horn 1220 , a phase plate 1240 and a circulator 1260 , The circulator 1250 is with the horn 1210 , the recipient 135a (R1) and the transmitter 130a (T1) connected. The circulator 1260 is with the horn 1220 , the recipient 135b (R2) and the transmitter 130b (T2) connected.

A phase plate 1230 is designed to illuminate one of the complementary subarray structures, while the other phase plate 1240 is designed to illuminate the other complementary subarray structure. At a Embodiments of a separate illumination mode are T2 130b and R1 135a selected to generate the separated signal, T1 130a is off and the signal from R2 135b is ignored. In another embodiment of the separate illumination mode, T1 130a and R2 135b selected to generate the separated signal, T2 130b is off and the signal from R1 135a is ignored. In the connected lighting mode, both transmitters 130a and 130b and both recipients 135a and 135b used to generate two connected signals (connected R1 and connected R2). The processor again determines the value of a pixel or voxel corresponding to the target by forming an appropriate complex linear combination of the three signals (separated, connected R1 and connected R2).

13 FIG. 12 is a schematic diagram of another example lighting system. FIG 100 capable of operating in multiple illumination modes, without switches, for use with the microwave imaging system 10 from 10 , at 13 includes the lighting system 100 a summing receiver (as receiver 135 and summing nodes 1380 shown), a transmitter 130 , Microwave horns 1310 and 1320 , Phase plates 1330 and 1340 , a 90 ° hybrid coupler 1350 , Circulator 1360 and variable (gain and phase) amplifiers 1370 , The circulator 1360 is with the transmitter 130 , the variable amplifier 1370 and the lower right arm 1354 of the 90 ° hybrid coupler 1350 connected. The summing receiver 135 and 1380 is with the variable gain amplifier 1370 and the lower left arm 1392 of the 90 ° hybrid coupler 1350 connected. The Horn 1310 is with the upper left arm 1356 of the 90 ° hybrid coupler 1350 connected, and the horn 1320 is with the upper right arm 1358 of the 90 ° hybrid coupler 1350 connected.

A phase plate 1330 is designed to illuminate one of the complementary subarray structures, while the other phase plate 1340 is designed to illuminate the other complementary subarray structure. In 13 For example, the connected and the separate illumination modes are performed substantially simultaneously, using a summing node 1380 , The variable amplifier 1370 provides a suitable linear combination of the "pure" and "mixed" signals which is equivalent to a linear combination of the combined and separate modes of the summing receiver 135 and 1380 , For example, to create a 50/50 Connected + Split distribution as shown in 14 is shown, the voltage gain should be set to three. In one embodiment, the summing receiver is 135 and 1380 implemented with analogue amplification and combination (as in 13 is shown). In a further embodiment, the summing receiver is 135 and 1380 implemented using two receivers followed by digital multiplication and addition. In yet another embodiment, a single receiver may be used and a single switch may either be the lower left arm 1352 of the 90 ° hybrid coupler 1350 or the lower left gate of the circulator 1360 select, followed by digital multiplication and addition.

15 is a flowchart that illustrates an example process 1500 for detecting a microwave image of a target on an object, according to embodiments of the present invention. Initially, at block 1510 an antenna array is provided comprising a plurality of antenna elements arranged in complementary subarray structures in a sparse geometry. At block 1510 Both complementary subarray structures of the antenna array are illuminated to direct a first transmit beam of microwave illumination to the target. After that, at block 1530 receive a first reflection beam of the reflected microwave illumination reflected by the target from both complementary subarray structures of the antenna array to produce a first receive signal in a first mode. At block 1540 a first of the complementary subarray structures of the antenna array is illuminated to direct a second transmit beam of the microwave illumination to the target. After that, at block 1550 receive a second reflection beam of the reflected microwave illumination from a second of the complementary subarray structures of the antenna array to produce a second receive signal in a second mode. Finally, at block 1560 the value of a pixel or voxel associated with the target, which represents an intensity of the reflected microwave illumination reflected from the target, determined as a linear combination of the first received signal and the second received signal. This process may be repeated for each pixel or voxel in the image, or alternatively, as associated with 16 and 17 to reduce the switching overhead, all the pixels or voxels in an image may be scanned in one illumination mode before switching to the other illumination mode.

16 is a flowchart that illustrates an example process 1600 for acquiring a microwave image of an object using a sparse antenna array comprising complementary subarray structures of antenna elements according to embodiments of the present invention. Initially, at block 1610 the microwave imaging system is set to a lighting mode (ie either connected or disconnected). In embodiments where switches are used to switch between the lighting modes, at block 1610 the switches are set to implement the first illumination mode. After that, at block 1620 each pixel or voxel in the microwave image of the object is scanned in the first illumination mode (ie, each target is imaged) to produce respective first-mode signals for each pixel or voxel. At block 1630 For example, each first mode signal is multiplied by a first multiplier which provides the corresponding weight to the first mode signals, and the resulting weighted first mode signals are latched in memory 1640 saved.

At block 1650 For example, the microwave imaging system is set to a second illumination mode (ie either connected or disconnected). For example, in an embodiment where the switches are used to switch between the illumination modes, block 1650 the switches are set to implement the second illumination mode. After that, at block 1660 each pixel or voxel in the microwave image of the object is scanned in the second illumination mode (ie, each target is imaged) to produce respective second-mode signals for each pixel or voxel. At block 1670 For example, each second mode signal is multiplied by a second multiplier which provides the corresponding weight to the second mode signals, and the resulting weighted second mode signals become the respective weighted first mode signals for each pixel or voxel block 1680 to generate a value for each pixel or voxel in the microwave image. At block 1690 For example, the microwave image of the object may be displayed using the pixel / voxel values. This process is included 1695 for each scanned object to generate a respective microwave image for each object.

17 is a flowchart illustrating another example process 1700 with reduced switching events between microwave images of objects detected using a sparse antenna array that includes complementary subarray structures of antenna elements, in accordance with embodiments of the present invention. Initially, at block 1710 an initial lighting mode (ie, either connected or disconnected) is selected as a current lighting mode, and a corresponding multiplier for the current mode is determined. After that, at block 1720 each pixel or voxel in the microwave image of the object is scanned in the current illumination mode (ie, each target is imaged) to produce respective first signals for each pixel or voxel. At block 1730 Each first signal is multiplied by the multiplier for the current mode, and the resulting weighted first signals become Block 1740 stored in the memory.

At block 1750 the other illumination mode (ie, either connected or disconnected) is selected as the current illumination mode, and at Block 1760 For example, each pixel or voxel in the microwave image of the object is scanned in the current illumination mode (ie, each target is imaged) to generate respective second signals for each pixel or voxel. At block 1770 For example, each second signal is multiplied by the current illumination mode multiplier and the resulting weighted second signals become the respective weighted first signals for each pixel or voxel at block 1780 to generate a value for each pixel or voxel in the microwave image. At block 1790 For example, the microwave image of the object may be displayed using the pixel / voxel values. This process is repeated at 1795 until block 1720 , in which the illumination mode, the second signals at block 1760 has generated at block 1720 is used as the current illumination mode for the next scanned object.

Claims (26)

Lighting system ( 100 ) in a microwave imaging system ( 10 ) for illuminating an antenna array ( 50 ), the antenna elements ( 80 ) for directing microwave illumination to and from a target ( 155 ) to obtain a microwave image of an object ( 150 ), wherein the antenna array ( 50 ) Subarrays ( 60 ) of the antenna elements ( 80 ) arranged in a sparse geometry to form complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ), the lighting system ( 100 ) comprises the following features: a transmitter ( 130 ), which is effective to transmit microwave illumination at frequencies between 1 GHz and 1000 GHz to the antenna array ( 50 ) transferred to; a receiver ( 135 ) effective to move from the antenna array ( 50 ) to receive reflected microwave light emitted by the target ( 155 ) is reflected; and a lighting network ( 140 ) which is operative in a first mode to control the microwave illumination ( 20 ) from the transmitter ( 130 ) to both of the complementary structures ( 90a . 90b ) of the antenna array ( 50 ), and the reflected microwave illumination ( 40 ) of both complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) to the recipient ( 135 ), the lighting network ( 140 ) is also operative in a second mode to control the Microwave lighting ( 30 ) from the transmitter ( 130 ) to a first of the complementary subarray structures ( 90a ) of the antenna array ( 50 ) and the reflected microwave illumination ( 70 ) of a second of the complementary subarray structures ( 90b ) of the antenna array ( 50 ) to the recipient ( 135 ) to deliver. Lighting system ( 100 ) according to claim 1, wherein the lighting network ( 140 ) at least two microwave horns ( 310 . 330 ) for illuminating the complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ). Lighting system ( 100 ) according to claim 2, wherein the lighting network ( 140 ) further a respective phase plate ( 340 . 344 ) for each of the at least two microwave horns ( 310 . 330 ), and wherein the respective phase plates are operative to generate complementary illumination structures to define the complementary structures ( 90a . 90b ) of the antenna array ( 50 ) to illuminate. The lighting system ( 100 ) according to claim 3, wherein the lighting network ( 140 ) a first microwave horn ( 310 ) operatively connected to a first phase plate ( 340 ) to form a first illumination structure for illuminating the first complementary subarray structure ( 90a ) of the antenna array ( 50 ), a second microwave horn ( 330 ) operatively connected to a second phase plate ( 344 ) is connected to a second illumination structure ( 90b ) for illuminating the second complementary subarray structure ( 90b ) of the antenna array ( 50 ) and a third microwave horn ( 320 ) operatively connected to a third phase plate ( 342 ) to form a third illumination structure for illuminating both complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) to create. Lighting system ( 100 ) according to claim 4, wherein the lighting network ( 140 ) a circulator ( 350 ), with the third horn ( 320 ), a first switch ( 360 ), with the recipient ( 135 ) and is arranged to be selectively connected to the circulator ( 350 ) in the first mode and the first horn ( 310 ) in the second mode, and a second switch ( 370 ) associated with the transmitter ( 130 ) and is arranged to be selectively connected to the circulator ( 350 ) in the first mode and the second horn ( 330 ) in the second mode. Lighting system ( 100 ) according to claim 3, wherein the lighting network ( 140 ) a first microwave horn ( 520 ) operatively connected to a solid phase plate to form a first illumination structure for illuminating the first complementary subarray structure (FIG. 90a ) of the antenna array ( 50 ) and a second microwave horn ( 510 ) operatively connected to a variable phase plate to form a second illumination structure for illuminating the second complementary subarray structure (FIG. 90b ) of the antenna array ( 50 ) and a third illumination structure for illuminating both complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) to create. Lighting system ( 100 ) according to claim 6, wherein the lighting network ( 140 ) a circulator ( 550 ) connected between the receiver and the second horn ( 510 ), and a switch ( 560 ) connected to the transmitter ( 130 ) and is arranged to be selectively connected to the circulator ( 550 ) in the first mode and the first horn ( 520 ) in the second mode. Lighting system ( 100 ) according to claim 3, wherein the lighting network ( 140 ) a first microwave horn ( 310 . 610 . 710 . 810 . 910 . 1110 . 1210 . 1310 ) operatively connected to a first phase plate to form a first illumination structure for illuminating the first complementary subarray structure (FIG. 90a ) of the antenna array ( 50 ) and a second microwave horn ( 320 . 620 . 720 . 820 . 920 . 1120 . 1220 . 1320 ) operatively connected to a second phase plate to form a second illumination structure for illuminating the second complementary subarray structure (FIG. 90b ) of the antenna array ( 50 ) to create. Lighting system ( 100 ) according to claim 8, wherein the lighting system ( 100 ) further comprises the following features: a power divider ( 650 ), with a circulator ( 660 ), a first switch connected to the receiver ( 135 ) and is arranged to be selectively connected to the circulator ( 660 ) in the first mode and the first horn ( 610 ) in the second mode, a second switch ( 685 ) connected to the transmitter ( 130 ) and is arranged to be selectively connected to the circulator ( 660 ) in the first mode and the second horn ( 620 ) in the second mode, a third switch ( 690 ), with the first horn ( 610 ) and is arranged to be selectively connected to the power divider ( 650 ) in the first mode and the receiver ( 135 ) in the second mode, and a fourth switch ( 695 ), with the second horn ( 620 ) and is arranged to be selectively connected to the power divider ( 650 ) in the first mode and the transmitter ( 130 ) in the second mode. Lighting system ( 100 ) according to claim 8, wherein the lighting network ( 140 ) further comprises the following features: a 90 ° hybrid coupler ( 750 ), a first switch ( 760 ), with the recipient ( 135 ) and is arranged to be selectively coupled to the 90 ° hybrid coupler ( 750 ) in the first mode and the first horn ( 710 ) in the second mode, a second switch ( 765 ) connected to the transmitter ( 130 ) and is arranged to be selectively coupled to the 90 ° hybrid coupler ( 750 ) in the first mode and the second horn ( 720 ) in the second mode, a third switch ( 770 ), with the first horn ( 710 ) and is arranged to be selectively coupled to the 90 ° hybrid coupler ( 750 ) in the first mode and the receiver ( 135 ) in the second mode, and a fourth switch ( 775 ), with the second horn ( 720 ) and arranged to selectively connect to the 90 ° hybrid coupler in the first mode and the transmitter ( 130 ) in the second mode. Lighting system ( 100 ) according to claim 8, wherein the lighting network ( 140 ) further comprises: a first circulator ( 860 ), with the first horn ( 810 ), a second circulator ( 870 ), with the second horn ( 820 ), a power divider ( 850 ) connected to the first circulator, the second circulator and a third circulator ( 865 ), a first switch ( 880 ), with the recipient ( 135 ) and is arranged to be selectively connected to the third circulator ( 865 ) in the first mode and the first circulator ( 860 ) in the second mode, and a second switch ( 890 ) connected to the transmitter ( 130 ) and is arranged to be selectively connected to the third circulator ( 865 ) in the first mode and the second circulator ( 870 ) in the second mode. Lighting system ( 100 ) according to claim 8, wherein the lighting network ( 140 ) further comprises: a first circulator ( 960 ), with the first horn ( 910 ), a second circulator ( 970 ), with the second horn ( 920 ), a 90 ° hybrid coupler ( 950 ), with the first circulator ( 960 ) and the second circulator ( 970 ), a first switch ( 980 ), with the recipient ( 135 ) and arranged to selectively connect to the 90 ° hybrid coupler in the first mode and the first circulator in the second mode, and a second switch ( 990 ) connected to the transmitter ( 130 ) and arranged to selectively connect to the 90 ° hybrid coupler in the first mode and the second circulator in the second mode. Lighting system ( 100 ) according to claim 8, in which the recipient ( 135 ) a first receiver ( 135a ) and a second receiver ( 135b ) and in which the lighting network ( 140 ) further comprises: a first circulator ( 1150 ), with the first horn ( 1110 ) and the first receiver ( 135a ), a second circulator ( 1160 ), with the second horn ( 1120 ) and the second receiver ( 135b ), a power divider ( 1170 ), which is connected to the first circulator, a first switch ( 1190 ) connected to the transmitter ( 130 ) and arranged to selectively connect to the power divider in the first mode and the second circulator in the second mode, and a second switch ( 1195 ), which is connected to the second circulator and arranged to be selectively connected to the power divider in the first mode and the transmitter ( 130 ) in the second mode. Lighting system ( 100 ) Claim 8, wherein the recipient ( 135 ) a first receiver ( 135a ) and a second receiver ( 135b ), the transmitter ( 130 ) a first transmitter ( 130a ) and a second transmitter ( 130b ), which are phase locked with respect to each other, and wherein the lighting network ( 140 ) a first circulator ( 1250 ), with the first horn ( 1210 ), the first recipient ( 135a ) and the first transmitter ( 130a ) and a second circulator ( 1260 ) connected to the second horn ( 1220 ), the second receiver ( 135b ) and the second transmitter ( 130b ) connected is. Lighting system ( 100 ) according to claim 8, wherein the lighting network ( 140 ) further comprises the following features: a circulator ( 1360 ) connected to the transmitter ( 130 ), an amplifier ( 1370 ) with variable gain, which is connected to the circulator, a summing node ( 1380 ) connected to the variable gain amplifier and the receiver ( 135 ) and a 90 ° hybrid coupler ( 1350 ), with the first horn ( 1310 ), the second horn ( 1320 ), the summing node and the circulator. Lighting system ( 100 ) according to one of claims 1 to 15, in which the lighting network ( 140 ) a first illumination optics ( 1030 ) and a second illumination optics ( 1040 ) and in which the transmitter ( 130 ) and the recipient ( 135 ) a first transceiver ( 1010 ) that interacts effectively with the first illumination optics ( 1030 ), and further comprising: a second transceiver 1020 ) operatively associated with the second illumination optics ( 1040 ) connected is. Microwave imaging system ( 10 ), comprising: an antenna array ( 50 ) comprising a plurality of antenna elements ( 80 ), each of the antenna elements ( 80 ) can be programmed with a respective direction coefficient to direct microwave illumination to and from a target ( 155 ), which the object ( 150 ), wherein the antenna array ( 50 ) Subarrays ( 60 ) of the antenna elements ( 80 ) arranged in a sparse geometry to form complementary subarray structures ( 90a and 90b ) of the antenna array ( 50 ) to build; a lighting system ( 100 ), which is effective to provide microwave illumination at frequencies between 1 GHz and 1000 GHz, to the complementary structures ( 90a . 90b ) of the antenna array ( 50 ) and to receive reflected microwave light emitted by the target ( 155 ) of the complementary subarray structures ( 90a and 90b ) of the antenna array ( 50 ) to receive a first received signal ( 170 ) in a first mode and a second received signal ( 175 ) in a second mode; and a processor ( 110 ), which is effective to give a value to the target ( 155 ) in a microwave image of the object ( 150 ) is assigned as a linear combination of the first received signal ( 170 ) and the second received signal ( 175 ). System according to claim 17, wherein the lighting system ( 100 ) is effective to combine both complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) and to receive reflected microwave light emitted by the target ( 155 ) of both complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) is reflected to the first received signal ( 170 ) and wherein the lighting system ( 100 ) is further effective to provide the microwave illumination to a first of the complementary subarray structures ( 90a ) of the antenna array ( 50 ) and the reflected microwave illumination from a second of the complementary subarray structures (FIG. 90b ) of the antenna array ( 50 ) to receive the second received signal ( 175 ) to create. A system according to claim 17 or 18, wherein each of the antenna elements ( 80 ) in the complementary subarray structures ( 90a . 90b ) is programmed with a respective first direction coefficient to enable microwave illumination from the target ( 155 ) to the lighting system ( 100 ) in the first mode, and each of the antenna elements ( 80 ) in one of the complementary subarray structures ( 90a . 90b ) is programmed with a respective second direction coefficient which is inverted with respect to the respective first direction coefficient in the second mode. A system according to any one of claims 17 to 19, wherein the complementary subarray structures form either a cross-shaped subarray structure or an image frame subarray structure. The system of any one of claims 17 to 20, wherein the processor is further operative to switch between the first mode and the second mode. A system according to any one of claims 17 to 21, wherein the processor is further operative to simultaneously receive the first receive signal (16). 170 ) and the second received signal ( 175 ) to recieve. A system according to claim 22, wherein the lighting system ( 100 ) a first receiver ( 135a ) adapted to receive the reflected microwave illumination to receive the second received signal ( 175 ) in the second mode, and a first portion of the first received signal ( 170 ) in the first mode, the illumination system ( 100 ) a second receiver ( 135b ) configured to receive the reflected microwave illumination to form a second portion of the first received signal (12). 170 ) in the first mode, and wherein the processor ( 110 ) is further operative for digital multiplication and addition of the first portion of the first received signal ( 170 ), the second portion of the first received signal ( 170 ) and the second received signal ( 175 ) to determine the value. A system according to any one of claims 17 to 23, further comprising: a display for displaying the microwave image of the object. Method for acquiring a microwave image of an object ( 150 ), comprising the steps of: providing an antenna array ( 50 ) comprising a plurality of antenna elements ( 80 ) for directing microwave illumination at frequencies between 1 GHz and 1000 GHz to and from a target ( 155 ), which is the object ( 150 ), wherein the antenna array ( 80 ) Subarrays ( 60 ) of the antenna elements ( 80 ) arranged in a sparse geometry to form complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) to build; Illuminate ( 1520 ) of both the complementary subarray structures ( 90a and 90b ) of the antenna array ( 50 ) to a first transmission beam ( 20 ) of the microwave lighting to the target ( 155 ) to judge; Receive ( 1530 ) of a first reflection beam ( 40 ) of the reflected microwave illumination passing through the target ( 155 ) of both of the complementary subarray structures ( 90a . 90b ) of the antenna array ( 50 ) to receive a first received signal ( 170 ) in a first mode; Illuminate ( 1540 ) of a first of the complementary subarray structures ( 90a ) of the antenna array ( 50 ) to a second transmission beam ( 30 ) of the microwave lighting to the target ( 155 ) to judge; Receive ( 1550 ) of a second reflection beam ( 70 ) of the reflected microwave illumination from a second of the complementary subarray structures ( 90b ) of the antenna array ( 50 ) to receive a second received signal ( 175 ) in a second mode; and determining ( 1560 ) an intensity of the reflected microwave illumination emitted by the target ( 155 ) is reflected as a linear combination of the first received signal ( 170 ) and the second received signal ( 175 ). The method of claim 25, wherein receiving the first received signal and receiving the second received signal are performed simultaneously.

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